Drive mechanisms employing gears and sprockets are well known. Such mechanisms have been used for operating garage doors, fire doors and more recently, for operating vehicle doors, especially, power sliding vehicle doors. Typically, a power sliding door unit incorporates a motor driving various coupled mechanisms such as a gear and sprocket arrangement to drive a chain for opening and closing the door. The chain may be secured at its two ends to opposing edges of the sliding door by a tension device, such as a spring, and a fastener, such as a pin.
Where the power sliding door unit and coupled mechanisms are operating properly, a user may simply open and close the sliding door by selectively controlling the motor driving the gear and sprocket. Where power fails or the unit otherwise becomes inoperative, the sliding door may nevertheless be manually opened or closed upon removal of the pin for detaching the chain from the door. However, once the chain has been detached, it may become entangled, rendering the task of reattaching the chain to the door difficult and cumbersome.
Release mechanisms for uncoupling chain-driven mechanisms are known. For example, U.S. Pat. No. 5,263,527 issued to Marlatt, et al., discloses a release mechanism including a pair of levers engaging a bearing disc to hold a toothed clutch in engagement between a shaft of a fire door and a shaft of its operator. Also, U.S. Pat. No. 5,048,653 issued to Fellows discloses a release apparatus for selectively connecting and disconnecting a sprocket drive wheel from a drive shaft by selectively thrusting a pair of sprag pins through registering openings in the sprocket wheel and into peripheral recesses in a collar secured to the drive shaft. These devices are often bulky and complex in structure. Moreover, where cooperating members are coupled by devices, such as pins, for joint rotation, the devices are often subjected to substantial deflection force and shear stress which break or otherwise deform the devices, shortening their life span.
Accordingly, there exists a demand for a simple, compact, yet sturdy, releasable drive mechanism, including a releasable drive mechanism for power sliding doors of vehicles, such as vans, buses, and the like. It is desired that such a releasable drive mechanism couple cooperating members in a manner minimizing wear and tear. It is also desired that such a releasable drive mechanism facilitates uncoupling as well as recoupling the cooperating members when desired.
In accordance with the present invention, a releasable drive mechanism is provided, having two cooperating members rotatable about a central axis, one of the cooperating members being rotatably secured to a shaft extending along the central axis, each of the cooperating members configured to provide at least a surface having a component or dimension parallel with the central axis that interfaces the surface of the other cooperating member, and a coupling member engageable with the cooperating members, the coupling member providing projections being positionable between the interfacing surfaces and movable relative to at least one of the interfacing surfaces for releasably coupling the cooperating members for joint rotation on the shaft. A means for disengaging the coupling member may also be provided. A biasing means may be further provided to facilitate engagement of the coupling member with the cooperating members.
These, as well as other features of the invention, will become apparent from the detailed description which follows, considered together with the appended drawings.